by Christopher Essex, Ross McKitrick, and Bjarne Andresen. They argue that the concept of a global temperature is ill-defined because it heavily depends on the choice of statistical methods. The choice of the methods is thus a political decision, not a part of the scientific method.

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The same points as made in the article, only very much more so, to any attempt to define a global temperature in the depth of winter at the height of the Cryogenian period, say 640 mya, when the earth was glaciated from poles to equator. Therefore any statement that the earth was colder then than it is now, and that there must have been a net warming to account for the difference, is inherently unprovable and is a political, not a climatological proposition.

But wait one moment! If you refer back three days or thereabouts you will see that you have established for the purpose of this blog that warming can be proved or disproved by looking to isolated daily temperature readings from Waterloo, Canada and "parts of Massachussetts". So we don't have to bother with the methodological point made by the paper (actually a worthy if pedestrian point which would be accepted by sensible climatologists on both sides of the argument) because of your unique insight that when Waterloo, Canada sneezes the world axiomatically catches cold. Well done!